Generally, fully automatic washing machines are products that remove a variety of dirt adhered to clothes, bedclothes and the like by using sulphurization of a detergent, frictional action of a water current, impact action applied to the laundry by a pulsator, and the like. According to the fully automatic washing machines, an amount and kind of laundry is sensed by means of a sensor and a washing mode is set automatically. A washing water is supplied up to an appropriate level according to an amount and kind of laundry and a washing operation is then performed under the control of a micro computer.
In addition, according to a conventional method for driving a fully automatic washing machine, a torque of a driving motor is transferred through a power transmission belt and a pulley to a washing shaft or a dewatering shaft, thereby rotating a pulsator or a dewatering tub.
Hereinafter, an operation of controlling a conventional washing machine will be described in brief.
First, if the user inputs a washing command, a laundry amount is sensed in an initial operation of the washing machine and washing water is supplied according to the sensed laundry amount. Then, a series of washing, rinsing and dewatering cycles are performed according to the sensed laundry amount. Meanwhile, a method using an applied power of the motor and the number of revolutions of the motor has been proposed for sensing the laundry amount in the initial operation of the washing machine.
However, in order to sense the number of revolutions of the motor, the belt and the pulley are intervened between the driving motor and the tub that receives the laundry, thereby causing a problem that an amount of rotation is not fully transferred to the motor. Therefore, there occurs an error in the laundry amount sensed by the number of revolutions of the motor. Further, there occurs a great error in the sensed laundry amount since an extension of the belt and a tension applied to the belt are different according to a temperature of the washing machine or a season.
Meanwhile, if necessary, the user opens the door of the washing machine and loads the laundry additionally during the washing operation. At this time, the related art has a disadvantage in that the user manipulates all washing cycles all over again in order to perform the washing cycles all over again. Further, in case the washing operations are performed successively and there is no additional water supply, the washing water is supplied less than an appropriate quantity. Therefore, there occurs a problem that degrades the washing performance or increases the washing load. Further, in case many loads are applied to the driving unit of the washing machine, parts may be degraded more seriously.